The present invention is directed to an improved "necked-down" can configuration and to an apparatus for spin flow forming of the "necked-down" end of the can. More particularly, the invention provides an apparatus to simultaneously form both a conical end in the can to provide a "necked-down" can and a false seam to improve the handling of the "necked-down" can during subsequent processing operations.
A "necked-down" can is a container with a tapered end portion to reduce the diameter of the open end of the can. Necked-down cans are useful in the production of cans having easy-open ends which ordinarily use removable lids having diameters which are less than the outer diameters of the cylindrical bodies forming the cans. The reduction of the container diameter to permit the utilization of smaller diameter, easy-open lids has been done for many years in the two-piece container industry. Both the configuration of the two-piece container and the materials and processes typically used to manufacture the container are amenable to the material manipulating methods required to form the tapered or conical container end.
In the food industry, the majority of the containers used to package food are three-piece cans comprising a thin wall, hollow cylindrical body and separate top and bottom covers. The cylindrical body is rolled from sheet material and fastened along a longitudinal seam which is typically soldered, welded or cemented. Moreover, the cans are ordinarily made from a material such as double reduced steel which, together with the longitudinal seam, make the forming of a reduced diameter end difficult. In addition, the processing of the food after packaging in the can requires an even rolling of the can through equipment which generally engages the can at rolling support areas which are most advantageously located along the circumferential seams arranged at the top and bottom of the can to secure the top and bottom covers to the cylindrical body.
When the top portion of the cylindrical body is tapered to reduce the open end diameter of the can, the can can no longer be supported for rolling in the advantageous horizontal position, but will slant within the processing equipment. Thus, necked-down cans do not roll evenly and are prone to damage such as flange splitting during processing and agitated retort cooking. The above-described difficulties and disadvantages in the manufacture and handling of necked-down, three-piece cans has, as a practical matter, precluded the widespread use of necked-down cans in the food industry. Accordingly, the food industry has not been able to make full use of advantageous, smaller diameter, easy-open lids.
An apparatus which is operable to form a smooth conical neck in the cylindrical body of a three-piece can is disclosed in U.S. Pat. No. 4,563,887. Pursuant to the disclosure of the aforementioned U.S. Patent, an externally disposed free roll is moved inward and axially against the outside wall of the open end of a rotatably mounted cylindrical body. The free roll co-operates with a spring loaded interior support and an axially offset interior sleeve member to form a smooth conical end on the cylindrical body in a single spin flow forming operation. Thus, the apparatus described in U.S. Pat. No. 4,563,887 provides a straightforward means to form a necked-down configuration in the cylindrical body of a three-piece can. However, while the disclosure of U.S. Pat. No. 4,563,887 removes the heretofore encountered difficulties in the formation of a necked-down, three-piece can, the problem of uneven rolling during further processing still exists.
It is, therefore, a primary objective of the present invention to overcome the uneven rolling problem by providing a method and apparatus to simultaneously form both a smooth conical end and a false seam in the three-piece can. Generally, the invention comprises a necked-down cylindrical body including a false seam adjacent the conical, reduced diameter end of the cylindrical body. The diameter of the false seam is formed to be equal to the diameter of the seam at the unreduced bottom end of the cylindrical body. In this manner, the processing equipment can engage the bottom seam and the false seam to achieve an even rolling of the can, as in the case of a conventional three-piece can. Significantly, the reduced diameter of the can permits the use of a smaller diameter, easy-open lid.
Pursuant to the apparatus of the invention, an externally disposed free roll is formed to a predetermined surface profile and is controllably movable inwardly and axially to engage the exterior surface of a cylindrical body mounted upon a holder for rotation. The free roll co-operates with an offset, axially fixed, rotary sleeve member mounted within the interior of the cylindrical body. The rotary sleeve member is also formed to a predetermined surface profile and is positioned such that the axial, inward movement of the free roll against the cylindrical body wall and the interior rotary sleeve member deforms the cylindrical body wall between the predetermined surface profiles of the free roll and the offset, rotary sleeve. The co-operating surface profiles of the free roll and rotary sleeve deform the cylindrical body surface adjacent one end thereof, as it rotates, to an outwardly extending, circumferential bulge portion that then extends conically to the outer, now reduced end of the cylindrical body.
In accordance with the invention, the circumferential bulge is formed by the predetermined, co-operating surface profiles to a diameter which is equal to the diameter of the double seam at the unreduced bottom end of the cylindrical body. Thus, the circumferential bulge forms the false seam of the invention and the bulge and bottom seam of the cylindrical can provide equal diameter rolling support areas for even rolling processing. Likewise, the predetermined, co-operating surface profiles form the conical end to reduce the open top diameter of the cylindrical body to a diameter which is suitable for advantageous use in connection with any easy-open lid.
For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description and to the accompanying drawings.